OSMOTIC ADJUSTMENT OF PLANTS TO SALINE MEDIA. I. STEADY STATE

Bernstein , Leon . (U. S. Salinity Lab., Riverside, Calif.) Osmotic adjustment of plants to saline media. I. Steady state. Amer. Jour. Bot. 48(10): 909–918. Illus. 1961.—The osmotic pressure (OP) of roots, as well as the OP of aboveground parts of cotton and pepper plants, increase pari passu with increases in the OP of the medium over as wide a range of salinity as would permit any growth. New plasmolytic and cryoscopic techniques yield comparable OP values for roots when dilution of cell sap by the free-space solution and by endosmosis during rinsing of roots are taken into account. Since OP differentials between plant parts and root media are maintained, turgor does not decrease and growth inhibition by salinity cannot be attributed to water stress in the sense of lowered plant turgor. Some alternative mechanisms for osmotic inhibition of growth are considered and the osmotic adjustment process itself is indicated as a likely limiting factor for growth under saline conditions. Osmotic adjustment of cells to salinity depends in part on increased accumulation of ions and also on substitution of monovalent for polyvalent ions. The relative importance of increased salt accumulation, ionic substitution and increased non-electrolyte concentration varies with organ (leaf or root), leaf age and salinity level.